Current MBRS-supported research by this Principal Investigator and his student research assistants has been directed toward identifying life-style risk factors for cardiovascular, pulmonary and other health effects among middle-aged Navajo Indians. Matched pairs of siblings have been selected as subjects, where the sibling pairs differ substantially between each other in life-style as a result of differing educational and employment histories. This project is now mid-way through the second year of research activity. A third year of support is required in order to complete the data collection and analysis of this project, in accordance with the original research plan. That "third year" constitutes "Year 1" in the current proposal. The second and third years of the current proposal involve re-directing our research focus from middle-aged Navajos to adolescent Navajos, and focusing particularly on the health effects of tobacco use within this younger age group. Whereas tobacco use by Navajos has been historically very low, a startling increase in tobacco use has been observed among the current generation of adolescent and young adult Navajos -- both involving smoking tobacco and chewing tobacco. Navajo students in the 7th grade, 10th grade and 12th grade at three public schools on the Navajo Nation (one "urban" school system and two "rural" school systems) will be interviewed to determine their patterns of tobacco use and to gather other pertinent demographic, social and health information. Health effects and correlates associated with tobacco use will be assessed by obtaining a variety of measurements on each student, including height, weight, blood pressure, pulse rate, lung capacities, skinfold thickness, and 24-hour dietary recall.